While working a summer job in college, I met a guy several years older than me who I was attracted to in an exciting and powerful can’t-eat-can’t-sleep kind of way.

If I was making copies and he happened to walk by and make eye contact with me, I would get a rush throughout my body that would make my cheeks flush and my knees buckle. With every text message he sent me, I would get a flutter of excitement in my stomach.

At age 20, I assumed the intensity of these feelings was a good sign ― isn’t this what the early stages of falling in love are supposed to feel like? Now, nearly a decade later, I realize I was just completely infatuated with this guy and that those intense feelings had a lot more to do with lust than love.

In the 1990s, a team of researchers led by biological anthropologist Helen Fisher examined the science behind lust and love. They divided romantic love into three distinct categories: lust, attraction and attachment, each associated with their own brain chemistry.

They found that lust, which is fueled by a yearning for sexual gratification, releases hormones like testosterone and estrogen that increase a person’s libido.

Attraction describes an infatuation that goes beyond sex ― for example, you can’t stop thinking about someone, you find yourself daydreaming about getting to know them and spending time with them, etc. That’s when neurotransmitters such as dopamine and norepinephrine are released, which can lead to feelings of elation, loss of appetite and decreased need for sleep.

The third category is attachment or “companionate love.” When compared to lust and attraction, attachment tends to be more secure, grounded and lasting. It releases bonding hormones such as oxytocin and vasopressin.

Brain chemistry aside, how can you tell if the sensations you’re feeling are more aligned with love, or with the more fleeting lust and attraction? To better understand some of the differences between them, we reached out to relationship experts. Here’s what they told us:

Lust is about a physical connection. Love is about an emotional connection.

“Lust feels like you intensely want to have sex with someone. Love feels like you want to have sex with someone and be emotionally close to them, too. Love means you want to spend time with your partner and listen to his or her needs and emotions to feel connected. You also are interested in meeting your beloved’s friends. Lust means you’re more interested in having sex than having intimate conversations or meeting the person’s friends.” ― Dr. Judith Orloff, psychiatrist and author of The Empath’s Survival Guide

Lust is impulsive. Love takes time.

“Love is rooted in delayed gratification, while lust is rooted in instant pleasure. Lust feels like sprinting; love feels like a marathon. Love means acceptance; lust means indulgence.” ― Janet Brito, a psychologist and sex therapist at the Center for Sexual and Reproductive Health

Lust skims the surface. Love goes deeper.

“Lust is a state of mind that focuses on body parts, seduction, power, fantasy and excitement. Love is risky and scary on an emotional level. You’re becoming very real and vulnerable with them, trusting them with your fears and hopes, sharing stories of shame and pride, hope and disappointment, and really letting yourself be known. Love is letting your guard down and granting your partner access to areas you don’t even like to visit.” ― Ryan Howes, clinical psychologist

Lust is short and sudden. Love is slow and steady.

“Love means hanging on for the long-distance ride. When lust is the primary driver, partners can literally be in and out in one night. Love is rooted in a deep commitment and endurance. Lust is rooted in a longing of the loins and often results in unsatisfying hook-ups. Love is a comforting pilot light that, if fed properly, can fuel a couple for a lifetime. Lust can lead to a roaring bonfire of sex, but sex without a real relationship quickly turns to ashes.” ― Iris Krasnow, author of Sex After: Women Share How Intimacy Changes As Life Changes

Love increases with time. Lust decreases with time.

“Love is rooted in attachment and bonding that grows over time. Lust is rooted in intense desire and fades over time. Lust feels like a rollercoaster of emotions driven by biological forces and activated by our reward center, driven by desire for pleasure and connection. Love feels like the desire and need for attachment with biological, sociocultural, and psychological factors that determine its development.” ― Shannon Chavez, psychologist and sex therapist

Lust is about you. Love is about them.

“When you lust for someone, you must have them. You need their body or presence in your life as if your life depends on it. Love is not possessive, though. You’ll certainly want someone you love in your life, but if their best life is found apart from you, then you want that for them. When you find that their well-being is a higher priority than your cravings, you’re in love.” ― Howes